Update UserCourseView instantaneously

[frederoni]

Fixes #1731

• Update UserCourseView instantaneously when a camera change is triggered by a user interaction.
• Update UserCourseView instantaneously when the map view’s layout margin changes.

Before	After

cc @1ec5 @vincethecoder @JThramer

[frederoni]

I would preferably avoid this frame by frame tracking but using updateCourseTracking(location:camera:animated:false) did not mitigate the lag/animation. cc @1ec5

[1ec5]

Perhaps there’s a race condition in which this method gets called before the map view updates its center coordinate to reflect the margin change, so that by the time we convert the user location to a center point within the (non)animation block, the center point still reflects the old margins.

mapbox-navigation-ios/MapboxNavigation/NavigationMapView.swift

Lines 332 to 334 in a0e5dbc

	UIView.animate(withDuration: duration, delay: 0, options: [.curveLinear, .beginFromCurrentState], animations: {
	self.userCourseView?.center = self.convert(location.coordinate, toPointTo: self)
	})

Temporarily enabling frame-by-frame course tracking ensures that the view moves as soon as the map adjusts to the new content insets (since that requires the map view to render another frame):

mapbox-navigation-ios/MapboxNavigation/NavigationMapView.swift

Lines 261 to 264 in a0e5dbc

	guard shouldPositionCourseViewFrameByFrame else { return }
	guard let location = userLocationForCourseTracking else { return }
	userCourseView?.center = convert(location.coordinate, toPointTo: self)

Temporarily reenabling frame-by-frame course tracking isn’t the end of the world, though if it really comes down to this race condition, then I’d think a shorter duration would still be sufficient to work around it.

[JThramer]

LGTM!

[1ec5]

Suggested changelog entry:

Fixed an issue causing UserCourseView to lag behind NavigationMapView whenever the map’s camera or content insets change significantly.

[1ec5]

Perhaps there’s a race condition in which this method gets called before the map view updates its center coordinate to reflect the margin change, so that by the time we convert the user location to a center point within the (non)animation block, the center point still reflects the old margins.

mapbox-navigation-ios/MapboxNavigation/NavigationMapView.swift

Lines 332 to 334 in a0e5dbc

	UIView.animate(withDuration: duration, delay: 0, options: [.curveLinear, .beginFromCurrentState], animations: {
	self.userCourseView?.center = self.convert(location.coordinate, toPointTo: self)
	})

Temporarily enabling frame-by-frame course tracking ensures that the view moves as soon as the map adjusts to the new content insets (since that requires the map view to render another frame):

mapbox-navigation-ios/MapboxNavigation/NavigationMapView.swift

Lines 261 to 264 in a0e5dbc

	guard shouldPositionCourseViewFrameByFrame else { return }
	guard let location = userLocationForCourseTracking else { return }
	userCourseView?.center = convert(location.coordinate, toPointTo: self)

Temporarily reenabling frame-by-frame course tracking isn’t the end of the world, though if it really comes down to this race condition, then I’d think a shorter duration would still be sufficient to work around it.